In the 1970s and 80s, crews sat at constant readiness in nuclear missile silos buried in the Arizona desert. What would have happened if they had got the order to launch?

Yvonne Morris had three minutes to get to work at the start of her shift. Any longer between phoning through her secret code at the perimeter gate and descending a set of stairs and she would have been arrested, at the very least.

Morris was one of the first female crew commanders of a Titan 2 nuclear missile silo. Stationed with the 390th Strategic Missile Wing in Tucson, Arizona between 1980 and 1984, she was responsible for three other crew members and a nine-megaton nuclear weapon.

Yvonne Morris was the commander in charge of the missile silo (BBC/Chris Hinkle)

“Even though our primary mission was peace through deterrence by preventing World War Three,” she says, “in the event we failed, we had to be ready to launch at all times in retaliation.”

From the early 1960s to the mid-80s, the city of Tucson was circled by 18 Titan 2 nuclear missile silos. Their location meant this and would have been a prime Soviet target. Today, only one silo remains – preserved as the Titan Missile Museum, a national monument with Morris as director. Time stopped here in 1982, preserving the site – complete with decommissioned missile – as a chilling reminder of cold war preparations for the end of the world.

“The three minutes to get to the silo is a built in security protocol,” Morris explains. “If we didn’t make it in three minutes, the crew underground assumes there is some sort of security situation topside.”

Crews came on duty for 24-hour shifts, or alerts, and began the day with a top secret security briefing at nearby Davis-Monthan airbase. It was a snapshot of the state of the world.

“I have to tell you, I slept better when I was on crew than I did today,” says Morris. “We were given excellent security briefings and so most days when I was driving out to the missile site, I was able to say to myself ‘today’s probably not going to be the day’.”

“That doesn’t mean,” she adds, “things can’t change in the blink of an eye, but in order to be effective at your job you have to let the possibility of Armageddon sit at the back of your brain.”

Half-a-mile or so from the main highway south to Mexico, the silo lies beneath a low mound surrounded by desert. The dusty slopes are dotted with cactus plants and there are signs warning of the danger of rattlesnakes. On the surface there is little to see behind the barbed-wire fence except a few low metal structures, the concrete launch doors, aerials and a staircase that disappears into the ground.

“A Titan 2 missile site is a lot like an iceberg,” says Morris. “Only about 10% of it is visible at the surface, the rest is underground.”

After descending the first flight of stairs, Morris would phone the control centre again. “They would release an electronic lock on the door and I’d pass into the entrapment area – really just a flight of stairs with a door at the top and bottom where I’d phone again with the entry code of the day.”

“They’re looking on CCTV to make sure I’m the only person there, that no-one is in there with me holding a gun to my head.”

The silo proper begins 10 metres underground behind a solid steel and concrete blast door. Hanging on two giant hinges, this 6,000lb (2.7 tonne) door is a foot (30cm) thick and twice the width of a regular doorway, but so well engineered you can push it open with a finger.

“From this point on we’re entering the hardened portion of the missile site – designed to withstand the effects of a nearby nuclear strike,” says Morris. “We weren’t designed to take a direct hit.”

The tunnel beyond is lined with metal girders, slung with rows of cables, and resembles the interior of a battleship or submarine. It leads to the launch control centre – a circular room with racks of equipment, vintage computer terminals, dials and switches. In the middle, a control console with a row of lights with a chair bolted to the floor in front of it.

“They wanted to put in substantial chairs for the two officers on the crew,” says Morris, “so they could ride out the shockwave of a nearby nuclear strike and still do their job.” In fact, the entire floor is mounted on giant shock absorbers and the light fittings hang on springs to cushion the effects of an attack.

At the back of the room is a red safe: the war safe. It contains the authenticator cards, with the codes needed to validate launch orders from the US president. The safe is secured by two combination padlocks belonging to the officers on duty. The crew coming off duty would swap their padlocks with the new crew. Only the individuals knew the four-digit combinations.

“It’s a pin number you have to be able to remember under extreme stress,” says Morris. “How many times have you been in line at the grocery store and can’t remember your pin? We have to be able to remember this code in a war situation.”

The floor above the control room has a rest area with bunks, kitchen and toilet. This is the only place in the complex where crew members were allowed on their own. Elsewhere they always had to be in sight of another crew member.

“The ‘no lone zone’ security process is a part of maintaining positive control of the nuclear weapon,” Morris explains. “You don’t want to give a single person access to the control room because you don’t want to give a single person the opportunity to launch the missile.”

This order led to some near farcical situations. For instance, the last duty any crew had to perform as part of their shift was to vacuum the 70s-era orange carpet in the control centre. The vacuum cleaner was stored behind the main control cabinets and retrieving it involved one person getting the cleaner, another person standing at the edge of the equipment racks and a third in the centre of the room. All ensuring they could see each other at all times.

In any normal shift, the primary duty of the crew was to check and maintain all the equipment in the silo, from the carpet to the missile itself – located 250 feet (76 metres) away at the end of another metal corridor, known as the long cableway.

The two-stage Titan 2 missile rises some seven storeys and has US Air Force helpfully painted on its side. The black casing at the top encloses the warhead, or re-entry vehicle (RV). Today it is empty but Morris remembers when, as a lieutenant on the crew, she saw it for the first time.

“The commander always arranged for a new crew member to perform an RV inspection on their first alert so they would come face to face with the missile,” Morris recalls. “So I’m nervous, I’m walking around and I saw that it had the manufacturer’s plate, General Electric, stamped on it.”

“There was a GE advert at the time which had the slogan ‘we bring good things to life’ and I couldn’t stop laughing,” she says. It was not the reaction the commander was hoping for.

What made the Titan 2 such an effective deterrent was its ability to launch in 58 seconds. The logic of Mutually Assured Destruction (Mad) depended on being able to respond to an enemy threat. “We both had enough missiles to destroy each other several times over and had the ability to detect a first strike and retaliate before that first strike would hit us,” says Morris. “The missiles would pass each other in the air like ships in the night, blow up both countries so there’re no survivors or anyone left to celebrate victory.” You can see why they called it Mad.

If the worst happened, the first the crew would know about it would be a warbling klaxon sounding around the silo. If they heard that, they all needed to run to the control centre to for a coded message broadcast from Strategic Air Command in Nebraska. There could be many reasons for the alarm to sound – a change of target, an increase in security procedures or the command from the President to launch the missile.

The message was broadcast as a series of letters and numbers, which the commander and deputy checked against a code book. If the codes indicated launch, they further authenticated them against the launch cards in the safe (which was protected by the two combination padlocks).

A code to unlock the missile had to be dialed into six thumbwheels of 16 numbers each on the equipment racks. The missile was launched by two separate keys (also kept in the safe), turned simultaneously and held for five seconds by the commander and deputy. Located on separate consoles, there is no way they could be operated by one person.

Sealed in their control room, the crew would not even hear the launch. So would Morris have turned the key?

“I’m 99.999% sure I would have done it,” she says. “My entire family lives in the foothills of Virginia, about 100 miles south of Washington DC, so by the time I get the launch order if they’re not already dead, they’re going to be dead soon.

“Life as I know it is over, when we get the launch order every horrible thing you’ve thought about Armageddon is about to happen and there was a part of me that was very motivated by the desire for retribution.”

By the time of launch, the crew themselves were only likely to survive a few minutes longer. The silo was not designed for a direct hit but – given that the Soviet Union knew exactly where they were – a missile was almost certainly on its way.

“The flight time between the Soviet Union and the US is 30 minutes,” says Morris. “Depending when we receive our launch order, that’s going to determine how much longer we have to live.”

Today, the silo is exactly how it was left in 1982. The Titan Missile Museum runs tours through the complex and you can stand at the top of the missile silo and look down through the duct.

For those of us who grew up during the Cold War, with the threat of nuclear conflict hanging over us, the silo remains a memorial to humanity’s ability to bring civilisation to an end. As relevant today as ever.

“The museum doesn’t advocate a position on nuclear weapons but we provide a framework for people to make up their own mind,” says Morris. “This missile site is playing just as an important role today because it remains the clearest, most accessible demonstration of the technology and the devastation it can cause.”